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BASE ENGINE MISFIRE WITH COOLANT CONSUMPTION BASE ENGINE MISFIRE WITH EXCESSIVE OIL CONSUMPTION assembly. Stuck valves Carbon buildup on the valve stem can cause the valve to not close properly. Repair or replace, as required. Excessively worn or mis-aligned timing chain Replace the timing chain and sprockets, as required. Worn camshaft lobes Replace the camshaft and valve lifters. Sticking lifters Replace, as required. Cut or damaged oil pump screen O-ring seal which may cause aeration of the engine oil Repair, as required. Refer to Oil Pressure Diagnosis and Testing. Improper operation of the camshaft position (CMP) actuator and/or control system Repair, as required. Refer to Camshaft Position Actuator and Solenoid Valve Diagnosis and Testing. Cause Correction Faulty cylinder head gaskets and/or cracking or other damage to the cylinder heads and engine block cooling system passages Coolant consumption may or may not cause the engine to overheat. 1. Inspect for spark plugs saturated by coolant. Refer to Spark Plug Inspection . 2. Perform a cylinder leak down test. Refer to Cylinder Leakage Test. 3. Inspect the cylinder heads and engine block for damage to the coolant passages and/or a faulty head gasket. Refer to Coolant in Combustion Chamber. 4. Repair or replace, as required. Cause Correction Worn valves, valve guides and/or valve stem oil seals 1. Inspect the spark plugs for oil deposits. Refer to Spark Plug Inspection . 2. Repair or replace, as required. Worn piston rings Oil consumption may or may not cause the 1. Inspect the spark plugs for oil deposits. Refer to Spark Plug Inspection .
2008 Hummer H2 2008 ENGINE Engine Mechanical - 6.2L - H2
ENGINE NOISE ON START-UP, BUT ONLY LASTING A FEW SECONDS UPPER ENGINE NOISE, REGARDLESS OF ENGINE SPEED engine to misfire. 2. Inspect the cylinders for a loss of compression. Refer to Engine Compression Test. 3. Perform cylinder leak down and compression testing to determine the cause. Refer to Cylinder Leakage Test. 4. Repair or replace, as required. Cause Correction Incorrect oil filter without anti-drainback feature Install the correct oil filter. Incorrect oil viscosity 1. Drain the oil. 2. Install the correct viscosity oil. High valve lifter leak down rate Replace the lifters, as required. Worn crankshaft thrust bearing 1. Inspect the crankshaft end play. 2. Inspect the thrust bearing and crankshaft. 3. Repair or replace, as required. Damaged or faulty oil filter bypass valve The bypass valve is now internal to the oil filter. 1. Inspect the oil filter bypass valve for proper operation. 2. Repair or replace, as required. Cause Correction Low oil pressure 1. Perform an oil pressure test. Refer to Oil Pressure Diagnosis and Testing. 2. Repair or replace, as required. Loose and/or worn valve rocker arm attachments 1. Inspect the valve rocker arm, bolt, and pedestal. 2. Repair or replace, as required. Worn or damaged valve rocker arm 1. Inspect the rocker arm for wear or missing needle bearings
2008 Hummer H2 2008 ENGINE Engine Mechanical - 6.2L - H2
2. Replace the valve rocker arms, as required. Bent or damaged push rod Inspect the following components and replace, as required: The valve rocker arm The valve push rod The valve lifter The valve lifter guide The piston
Inspect the top of the pistons for valve contact. If the top of the piston shows valve contact, replace the piston and pin assembly. Improper lubrication to the valve rocker arms Inspect the following components and repair or replace, as required: The valve rocker arm The valve push rod The valve lifter The oil filter bypass valve The oil pump and pump screen The engine block oil galleries Broken valve spring Replace the valve spring and spring shim. Worn or dirty valve lifters Replace the valve lifters, as required. Improper operation of the camshaft position (CMP) actuator and/or control system Repair, as required. Refer to Camshaft Position Actuator and Solenoid Valve Diagnosis and Testing. Stretched or broken timing chain and/or damaged sprocket teeth Replace the timing chain and sprockets. Worn engine camshaft lobes 1. Inspect the engine camshaft lobes. 2. Replace the camshaft and valve lifters, as required. Worn valve guides or valve stems Inspect the following components and repair, as required:
2008 Hummer H2 2008 ENGINE Engine Mechanical - 6.2L - H2
LOWER ENGINE NOISE, REGARDLESS OF ENGINE SPEED The valves The valve guides Stuck valves Carbon on the valve stem or valve seat may cause the valve to stay open. Inspect the following components and repair, as required: The valves The valve guides Cut or damaged oil pump screen O-ring seal which may cause aeration of the engine oil Repair, as required. Refer to Oil Pressure Diagnosis and Testing. Cause Correction Low oil pressure 1. Perform an oil pressure test. Refer to Oil Pressure Diagnosis and Testing. 2. Repair or replace damaged components, as required. Worn accessory drive components Abnormalities such as severe cracking, bumps or missing areas in the accessory drive belt and/or misalignment of system components. 1. Inspect the accessory drive system. 2. Repair or replace, as required. Loose or damaged crankshaft balancer 1. Inspect the crankshaft balancer. 2. Repair or replace, as required. Detonation or spark knock Verify the correct operation of the ignition controls system. Refer to Symptoms - Engine Controls . Loose torque converter bolts 1. Inspect the torque converter bolts and flex plate. 2. Repair or replace, as required. Loose or damaged flywheel or flex plate Repair or replace the flywheel or flex plate. Oil pump screen loose, damaged, or restricted 1. Inspect the oil pump screen. 2. Repair or replace, as required. Excessive piston-to-cylinder bore clearance 1. Inspect the piston and cylinder bore. 2. Repair, as required.
2008 Hummer H2 2008 ENGINE Engine Mechanical - 6.2L - H2
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